North Carolina Cooperative Extension Service
North Carolina State University

Pesticide Note Number 6
ENT/pia-6
February 1996

Insect Management by North Carolina Potato Growers in 1994

Kenneth A. Sorensen, Extension Vegetable Entomology Specialist

The information and recommendations in this Note were developed for North Carolina and may not apply in other areas.

Introduction

The commercial production of potatoes in North Carolina is mostly
concentrated in nine counties in the coastal region of the state
(Sanders et al. 1995). Most of the crop is planted in March and
harvested in June and July. Atlantic and Superior are the primary
varieties of potato grown in North Carolina. Approximately sixty-five percent of the crop is sold for processing into potato chips,
with the remaining sold for fresh market. In 1994, 3,186,000 cwt.
of potatoes were produced on 18,400 acres in North Carolina (Watson
1995). The value of the potatoes produced in the state in 1994 was
estimated at $23.5 million.

Pest problems confronting potato growers in North Carolina
include weeds, nematodes, plant diseases and insects. Growers in
the state employ a variety of chemical and nonchemical pest
management practices to manage pests. Insect pests of economic
concern in North Carolina are Colorado potato beetles, European
corn borers, aphids, blister beetles, flea beetles, leafhoppers and
wireworms.

A mail survey of potato growers in fourteen counties in North
Carolina was conducted in the winter of 1995 to determine the pest
management practices used by the growers on the 1994 crop. Insect
management practices used by survey respondents in 1994 are
compared to results from a similar grower survey conducted for the
1989 potato crop (Toth et al. 1993).

Survey Method

Ninety-five potato growers in Beaufort, Camden, Carteret,
Chowan, Currituck, Henderson, Hyde, Johnston, Lenoir, Pamlico,
Pasquotank, Sampson, Tyrrell and Washington Counties (Fig. 1) were
surveyed by mail in January and February 1995, following methods
described by Christenson (1975) and Dillman (1978). All commercial
potato growers in these counties who were included on mailing lists
provided by the respective county extension centers and the North
Carolina Potato Association were surveyed.

On January 31, a sixteen page survey questionnaire accompanied
by a cover letter and pre-stamped return envelope was mailed to
each potato grower from their respective county extension centers.
On February 7, a postcard was sent to each grower as a reminder to
complete and return the questionnaire. Finally, on February 21,
another letter, questionnaire and pre-stamped return envelope was
sent to those growers not responding to previous correspondences.
Information contained in the survey questionnaires returned by
potato growers was compiled and analyzed in the Department of
Entomology at North Carolina State University.

Results and Discussion

Potato Production. Sixty-four (67%) of the 95 potato
producers surveyed responded. A total of 52 respondents planted
14,156.65 acres of potatoes in 1994, while the remaining
respondents did not produce a potato crop. Potato growers
responding to the survey harvested 13,938.35 acres of potatoes in
1994. The average yield of those growers returning questionnaires
was 199.24 cwt. per acre. Approximately 18,400 acres of potatoes
were harvested in North Carolina in 1994 (Watson 1995). The
statewide average yield of potatoes in 1994 was 173 cwt. per acre.

Colorado Potato Beetles. The Colorado potato beetle is the
most important insect pest on potatoes in North Carolina. Adult
feeding on potato plant foliage is seldom damaging; however, larvae
can cause extensive defoliation resulting in significant yield
losses.

Asana XL was the primary insecticide used for Colorado potato
beetle management on potatoes in 1994. Potato growers treated 72%
of the acreage with Asana XL (Fig. 2). Furadan and Thimet were
used by growers in 1994 on 26 and 24% of the acreage, respectively.
Other insecticides used in 1994 include Monitor, M-Trak, Ambush,
Vydate, Pounce and Guthion. Higher percentages of the potato
acreage were treated with Asana XL, Monitor, M-Trak and Vydate in
1994 than in 1989. Furadan, Thimet, Ambush, Pounce and Guthion
were applied to more acreage in 1989.

Seventy percent of the potato growers surveyed felt that
Colorado potato beetles in their potato crop had developed
resistance to insecticides in 1994; up from 58% in 1989. Thirty
percent of potato growers claimed that Furadan was no longer
effective against Colorado potato beetles in 1989, while 10 to 25%
of growers reported Sevin, Pydrin and Guthion as ineffective (Fig.
3). In 1994, Sevin and Furadan were considered no longer effective
on Colorado potato beetles by over 40% of growers. Between 10 and
25% of growers reported beetle resistance to Guthion, Thiodan,
Asana XL, Monitor, Ambush, Thimet and Vydate in 1994.

Fig. 3. Insecticides no longer effective against Colorado potato beetles according to North Carolina potato growers. Bars indicate the percentage of potato growers who found the insecticides ineffective in 1994 (dark) and 1989 (hatched) (Toth et al. 1993).

European Corn Borers. The European corn borer is a common
stem-boring pest of potatoes in eastern North Carolina. This
insect continues to cause concern among growers of fresh market
potatoes. Monitor, Furadan and Asana XL were used by potato
growers on 27, 24 and 17% of the acreage, respectively, to manage
European corn borers in 1994 (Fig. 4). Growers also used Ambush
and Guthion for the management of this pest. Compared to 1989, the
percentage of potato acreage treated with Monitor and Asana XL was
significantly higher in 1994, whereas the percentage of acres
treated with Furadan, Ambush and Guthion was lower. Pydrin and
Pounce were no longer used by potato growers for European corn
borers in 1994.

Fig. 4. Insecticides applied to manage European corn borers on potatoes in North Carolina. Bars indicate the percentage of potato acreage treated in 1994 (dark) and 1989 (hatched) (Toth et al. 1993) with the respective insecticides.

Other Insect Pests. Wireworms (i.e., corn wireworms, tobacco
wireworms and southern potato wireworms) may attack seed pieces at
planting or tubers late in the season. Their damage can result in
reduced plant stands or rejection of loads of potatoes by
processors. Aphids (potato, green peach and other species) are
sporadic pests of potatoes. Aphid feeding causes little damage in
potatoes; however, the spread of plant viruses by aphid vectors can
be of some concern to growers. Flea beetles and leafhoppers are
minor pests of potatoes and are usually addressed through
management techniques used for the major insect pests.

The use of Thimet, Di-Syston and Vydate for the management of
foliar-feeding insects and wireworms on potatoes has increased
since 1989 (Fig. 5). Potato growers treated about 40% of their
acreage in 1994 with Thimet. Problems with wireworms have been
responsible for the use of granular soil insecticides. Some early
season management of insects is also obtained through the
application of soil insecticides to potato fields.

Nonchemical Pest Management Practices. Potato growers were
asked to indicate on the survey questionnaire the nonchemical pest
management practices they used in 1994. Seventy-six percent of the
growers responded that they, a family member and/or an employee
scouted their potato fields for weeds, insects or plant diseases
(Fig. 6). Nearly 39% reported that a professional scout or
consultant performed this service. One grower indicated that a
county extension agent scouted his potatoes. Similarly, 76% of
potato growers reported that they, a family member or employee
scouted their potatoes in 1989, while 24% used a professional
scout. Slightly less than 2% of potato growers did not have their
potato fields scouted for weeds, insects or plant diseases in 1989.

Approximately 86% of potato growers indicated that they
rotated the fields on which they planted potatoes as a means of
pest management in 1994, up from 74% in 1989 (Fig.6). Corn and
soybeans were the predominant crops rotated with potatoes in 1989
and 1994. Seventy-four percent of potato growers applied different
insecticides to reduce Colorado potato beetle resistance in 1994;
85% of growers claimed to use this practice in 1989. A Colorado
potato beetle resistance monitoring kit developed in the Department
of Entomology at North Carolina State University was used by 28% of
growers in 1994, compared to 16% of growers in 1989.

Published by North Carolina Cooperative Extension Service

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